1. Field of the Invention
The present invention generally relates to a pixel structure, a driving method thereof, a pixel array structure, in particular and a liquid crystal display panel, to a pixel structure, a driving method thereof, a pixel array structure and a liquid crystal display panel having good display quality.
2. Description of Related Art
Thin film transistor liquid crystal display (TFT-LCD) has gradually become the mainstream in today's display market due to its characteristics such as high display quality, high space efficiency, low power consumption, and no radiation. Presently, the design of LCD is going towards high contrast ratio, rapid response, and wide viewing angle, wherein multi-domain vertically alignment (MVA)-LCD and in-plate switching (IPS) LCD are usually adopted to achieve wide-viewing angle display.
Even though wide-viewing angle display can be achieved by a MVA-LCD, color washout, namely, color shift, is usually produced in an image displayed by the MVA-LCD when a user looks at the image from a large viewing angle. FIG. 1 is a graph illustrating various γ (gamma) curves observed from different viewing angles (θ) of a conventional MVA LCD. Referring to FIG. 1, the ordinate axis represents transmittance, and the abscissa axis represents gray level, wherein the curve having γ=2.2 is an ideal curve. As shown in FIG. 1, the larger the viewing angle is (for example, θ=60°), the more the γ curve is deformed, namely, the further the γ curve is away from the ideal curve. To be specific, color shift will be produced in an image viewed from a large viewing angle because the image has high luminance at medium to low gray level from the large viewing angle. An existing method for reducing color shift is to align liquid crystal molecules at many different angles and divide each pixel into two sub display regions having different display voltages.
FIG. 2 is an equivalent circuit diagram of a conventional pixel structure with color washout solution. Referring to FIG. 2, the pixel structure 100 is electrically connected to a data line 102 and a scan line 104. The pixel structure 100 includes a first active device 110, a second active device 112, a first capacitance electrode 114, a second capacitance electrode 116, a first pixel electrode 120, and a second pixel electrode 130. The first pixel electrode 120 and the second pixel electrode 130 are respectively connected to the first active device 110 and the second active device 112 electrically. The first capacitance electrode 114 and the second capacitance electrode 116 respectively have a specific voltage level. Thus, the first pixel electrode 120 and the second pixel electrode 130 have different display voltages due to the capacitance coupling effect thereof with respectively the first capacitance electrode 114 and the second capacitance electrode 116. Accordingly, at medium to low gray level, one of the regions of the first pixel electrode 120 and the second pixel electrode 130 can have low luminance, while at high gray level, both the regions of the first pixel electrode 120 and the second pixel electrode 130 can have similar luminance. As a result, color shift produced at large viewing angle is restrained in the pixel structure 100.
However, the first pixel electrode 120 and the second pixel electrode 130 have to be arranged in a lattice pattern since they have to be disposed corresponding to capacitance electrodes (114 and 116) having different voltage levels, so that when the pixel structure 100 is provided in an LCD, images displayed in the LCD may look coarse-grained. Thereby, the display quality of the pixel structure 100 is still unsatisfactory.